Lecture 4-9 (Soils) Flashcards
What type of nutrient disorders can occur?
- Too much- Nutrient toxicity
2. Too little- Nutrient Deficiency
What macronutrients are toxic?
Fe, Mn, B, Cu, Cl in acidic conditions, Mo in Alkaline conditions
Name the most Deficient and least deficient Nutrients for manitoba
Most- Nitrogen, Phosphorus, Potassium
Least- Carbon, Oxygen, Hydrogen
Before applying a micronutrient what must you do? (6)
- Visual diagnosis
- eliminate other causes of poor growth
- consider crop and soil type for susceptibility
- verify the visual diagnosis
- Test application of micronutrients
- Prevent nutrient deficiencies
What is more common in a micronutrient disorder? Toxicity or Deficiency
Deficiency
What is over application of fertilizer? (3)
1- uneconomical
2- Possible pollution source
3- Possible toxic source
Where do you find the following deficiencies?
Iron-
Boron-
Zinc&Manganese -
Iron= Parts of Manitoba Boron= Saline soils Zine&manganese= Usually not a problem in Manitoba
What causes flax yellowing and low levels of these makes Flax more sensitive.
Iron causes the yellowing.
Low levels of Iron and Zinz
Why are salt blocks blue?
Because they contain copper sulfate
What are the most common micronutrient disorders related to?
Acidic Soils and Peat Soils
A low amount of what in an animal causes growth and bone deformation?
Molybdenum relative to copper
Why not add concentrated acid to soil? (5)
1- Dangerous 2- loss of lime and buffering capacity 3- death of crop upon spraying 4- Aluminium toxicity 5- Induced micronutrient toxicity
What is liming used for?
to increase pH
What is the most efficient use of lime?
apply small amounts every year or 2
Lime is neutralized or lost by; (5)
- Acid forming fertilizers
- acid formed by C02 and H20
-Leaching
Harvesting crops or grazing
-Erosion
-Acids dissolved in rainfall
Define Aggregate
A structural unit composed of many soil particles held together by binding agents
What is the equation for Soil aggregates
Primary properties + binding agents
What is soil structure?
The arrangements of sand, silt and clay into aggregates
What are the effects of soil structure on crop productivity? (5)
1- Risk of erosion 2- Aeration and ease of root growth 3- water infiltration rates 4- water retention 5- nutrient content and availability
why does soil structure vary from location to location? (6)
1- amount and activity of soil organisms
2- Parent material and nature of binding agents
3- Frequency and intensity of wetting and drying cycles
4- Tillage
5- crop rotation
6- sodicity
What are the 2 types of soil structures?
Structure less soil and Structured soil
Name the 2 structureless soils
single grained
massive
Name the 6 structured soils
- Granular
- Angular blocky (rectangle)
- Sub-angular blocky
- Prismatic
- Columnar
- Platy
Characteristics of Saline Soils (3)
- Good soil structure
- good drainage and water retention
- Good nutrient availability
Characteristics of sodic soils (3)
- Very poor structure
- Poor drainage
- Poor nutrient availability
What is Salinity?
Refers to a condition of soil in which water soluble soils are present in sufficient amounts to affect growth
Salinity problems occur in areas with restricted drainage due to? (4)
- High water tables
- surface ponding
- depressed areas
- very low pH
How serious is salinity?
Depends on the type of soil
Why does salinity occur?
Because there is salt all water including rainfall and it accumulates in the soil over time
Soils with too much sodium becomes; (3)
- Almost impermeable to water and puddles when driven on
- dries to an extremely hard crust
- Hard columnar structures form in the horizon
What are the 3 salts and the impact they have on crop growth;
- Calcium sulphate- No impact
- Magnesium Suphate- Adverse impact
- Sodium chloride- Serious impact
What is the impact of Salinity and Sodicity? (4)
- Decreased ability to absorb water and nutrients
- Salt toxicity
- Loss of plant available phosphorus
- Poor soil structure and crusting
5 main Characteristics of Salinity
- Topography
- Excess moisture
- Distinctive Vegetative growth
- soil color and structure
- Reduced crop and yields
How do you measure soil salinity?
By the electrical conductivity
How to sample?
- sample at 3 depths (0-6, 6-12, 12-24inches)
- Do not mix samples
3 Do not take sample from poor producing areas
Explain the 3 types of Salinity:
- 2-4ms/cm slightly saline
- 4-8mS/cm Moderately saline
- 8-16mS/cm Severly Saline
List the 8 ways of preventing Salinity;
- Summerfallow
- Forages
- Avoid burning
- Improve Drainage
- Manure and Crop residue
- Avoid deep tillage
- seed shallow
- Reduce weed competition
How is fertilizer made?
By combining Nitrogen from the atmosphere with hydrogen
What happens when you apply too little and too much Fertilizer?
Too little= Loss of money, poor yield, and yellowing of leaves
Too much= Loss of money, lodging, and environmental pollution